Field of the Invention
The present invention relates to an image generating apparatus and an image generating method.
Description of the Related Art
Currently an image generating method using light field rendering is progressing. According to this method, information on light in many directions in a three-dimensional space is recorded, and various images are generated by combining this information with image processing. A light field camera was implemented using this technique. In a light field camera, many micro-lens arrays are disposed between the lens and an image sensor, for example, so as to record information on light from many directions. An advantage of this light field camera is that the user can freely set a blur amount and a focus of a photograph after imaging. However, compared with a standard camera, image quality is not very good.
On the other hand, Non-patent literature (NPL) 1, for example, a method for generating an image equivalent to that of the light field camera using a standard digital camera and the like was disclosed. According to this method, a defocused image group is acquired by imaging one object with changing a focus, and a position-invariant linear filter processing is performed on the image group, whereby each image having a different view point, blur amount, blur shape and focus can be generated. According to this method, an image is generated by a simple filter processing without performing complicated determination processing that considers where and how a blur occurred, hence a desired image can be stably generated. In this method, a position-invariant three-dimensional blur function must be provided for approximating the blur characteristic of the imaging optical system, but even if the provided three-dimensional blur function and actual blur characteristic deviate for any reason, it is known that a major problem does not occur to the generated image. This characteristic makes it possible to generate high quality images simply and stably. The final image generated like this is hereafter called a “reconstructed image”. And the processing of generating the reconstructed image is called “image reconstruction”.
[NPL 1] Kazuya Kodama and Akira Kubota: “Efficient Reconstruction of All-in-Focus Images Through Shifted Pinholes from Multi-Focus Images for Dense Light Field Synthesis and Rendering”, IEEE Transactions on Image Processing, vol. 22, No. 11, pp. 4407-4421 (2013).
[NPL 2] Xi Ou, Takayuki Hamamoto, Akira Kubota, and Kazuya Kodama: “Efficient Free Viewpoint Image Acquisition From Multiple Differently Focused Images”, Visual Communications and Image Processing 2008 (VCIP 2008), SPIE Vol. 6822-73 (2008).